In the freight transportation field it is conventional practice to place cargo items in relatively large containers, and to load the containers onto flat beds or trailers or railroad cars. The corners of these large containers are defined by hollow block-like castings having slot-type openings in their lower faces. At selected points along the length of the vehicle bed there are usually disposed certain upstanding lock pins; each lock pin has an enlarged non-circular head for entry into one of the hollow castings at the corner of a freight container. The lock pins are spaced so that when the container is lowered onto the vehicle bed the upstanding lock pins automatically enter the slot type openings in the container corner castings. Each lock pin can be turned around its vertical axis so that its non-circular head overlies the casting lower wall, thereby locking the container against upward dislocation from the bed. U.S. Pat. No. 3,317,219 shows one form that such lock pins can take.
Freight containers have standard heights of eight feet and standard widths of eight feet. However the length can vary with different usage requirements; e.g. military transport containers are commonly either twenty feet long or ten feet long or 6 feet, 8 inches long. The length dimensions for the shorter containers are selected as even fractions of the longest container module length, whereby a twenty foot trailer can be used to handle different container combinations, such as one full length container or two 10-foot containers, or three of the smallest length containers.
Each container, whatever its length, must be anchored to the bed at all four of the container bottom corners. At least some of the anchoring or locking pins must therefore be either detachably or retractibly mounted on the vehicle bed in order that the containers or other cargo items will avoid striking portions of the non-used pins that would otherwise project above the bed surface.
An object of the present invention is to provide container twist locks that can be detachably mounted on the vehicle bed, thereby enabling the bed surface to be unobstructed by the presence of non-used locks. Other objects are to provide twist lock constructions that are relatively rigid and free from excessive wobble or play when mounted on the vehicle bed. Additional objects are to provide removable twist locks that are light weight, low cost, and small size. A particular object is to provide twist locks that do not project downwardly below the vehicle bed thickness, where they could strike tires or other structures such as suspension components, tail lights, support framework, etc.
The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without payment to me of any royalty thereon.